1. Field of the Invention
The present invention relates to a method of and an apparatus for applying laser beams emitted from a plurality of laser oscillators to respective regions of a workpiece to weld those regions.
2. Description of the Related Art
It has been attempted to weld inner and outer panels of an automobile body with a laser beam welding robot rather than a resistance spot welding robot. For examples Japanese laid-open patent publication No. 4-220187 discloses a laser beam welding robot having a laser beam applying head mounted on the distal end of a robot arm, the laser beam applying head being movable closely to a region of a workpiece which is to be welded for welding the workpiece.
However, since the laser beam applying head is positioned closely to the region of the workpiece to be welded, it is difficult to move the laser beam applying head at a high speed.
Another welding apparatus disclosed in Japanese patent publication No. 4-36792 has a plurality of welding heads disposed closely to a region of a workpiece which is to be welded. A desired one of the welding heads is selected by adjusting the angle of a plane mirror, and a laser beam is applied via the selected welding head to the region of the workpiece to be welded for thereby welding the workpiece.
The disclosed welding apparatus has a plurality of laser oscillators to be associated with all regions of a workpiece which are to be welded. If one of the laser oscillators fails to operate due to a malfunction, then the welding process in the region covered by the malfunctioning laser oscillator is interrupted. Therefore, in the event of a failure of one of the laser oscillators, the entire welding line that is combined with the welding apparatus needs to be shut down. Since it is time-consuming to repair or replace the malfunctioning laser oscillator, the entire welding line is made less efficient than it should be.